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Wednesday, November 30, 2011

E-Flite Cap 232 BP ARF - Flight Review

***** SAFETY WARNING *****
This product contains a manufacturing defect that makes it extremely dangerous to fly.  The hybrid carbon fiber/metal pushrod design is unsafe causing the binding between the metal and the carbon fiber to break loose under aerodynamic stress, causing the model to go out of control.  You MUST glue not only the clevis to the carbon fiber rod, as instructed in the manual, but also glue both ends of the black binding that holds the metal portion of the pushrod to the carbon fiber to prevent slippage in the air--which is not indicated in the manual. Horizon Hobby has been notified to pull the E-Flite Cap 232 off the shelves and recall all models until this unsafe defect is remedied.
At the 3 minute mark, a series of tight outside loops causes the factory supplied carbon/metal pushrod binding to slip (lengthening the pushrod in the air). I had to manually hold 95% down elevator + full down trim (indicated by the beeping in the video) to land the model. I erroneously thought the battery had slipped and moved the CG too far aft.  The manual calls for gluing the clevis to the carbon, but nowhere does it instruct one to glue this unsafe defective part.
-----End Update-----

I picked up this little "Cap 232" for $120 minus $25 in "store discounts" because Horizon Hobby forbids price competition.  ARF cost = $95. 
The E-Flite "Cap 232" is a proprietary, no-to-scale 
big wing RC 3D aerobat.  Sheeze, the cartoon 
canopy isn't even in the right place.
On the Ground:

The plane's name is in quotes 'cause it neither looks nor flies anything like a Cap 232.  Yeah, I know that there is a long tradition of naming proprietary RC airplanes after actual aircraft to which they bear little resemblance and share few major design features; usually they are minibats like this one, although the E-Flite Carbon Z Yak 54 set a new low standard for mos-characterizing larger airplanes.  Just because everyone does it, I don't accept it.  It's never worked for me, "but officer, surely you know that everyone speeds on this road."  It's lame to call an airplane something it is clearly not.
Real Cap 232's looks different and 
can accommodate 3D people
But I figured, hey, free motor, because E-flite boofed their Ascent's included 450 power system by including a way too heavy and strong 450 that also requires too much battery.  I replaced it with a drop-in 370.  450 now sitting in a drawer, and the Cap 232 recommended a 450, so you know, a lot like Charlie Brown charging Lucy holding a football, I skeptically bit.  
The plane turned out to be a great flyer.  The motor turned out to be another cludo recommendation - this time, too weak and/or too heavy on the denominator (T:W).

The informed might  be thinking, wait a second, the Cap 232 is lighter than the Ascent, so how can the motor be way too strong for a 19 oz motor glider and too weak for a 15 oz 3D aerobat.  Thing is, this isn't your average scale ultimate aerobat, the Cap 232 is a 425 sq in, 15 oz extreme machine.  Ok I know it is called a Cap 232, but lets get real, this unique RC design has wings, and that's where any serious resemblance to a Cap 232 ends.  The name is probably so E-flight can sell a few more airplanes to people who might like Cap 232s.  Fact is, this plane needs a 3D capable T:W, and it needs it bad.

That all said, this E-Flight thingamajobber is a super light, super low wingloading 3D'er.   The immoral Chinese sweatshop did a great job keeping the construction light and strong.  The plane comes with a beautifully covered single piece wing, incredibly light for the strength and stiffness.  The flat fuselage is built-up from balsa and plywood strips - it could have used some carbon fiber for strength and rigidity - it has some flex and seems a bit flimsy for the recommended power system.

The result of the skimpy fuselage and super light wing single-piece wing construction is an bare airframe weight of 8 oz.  That's not a typo, yes,  this plane manages 425 sq inches of wing area in an 8 oz balsa and ply airframe.  WCL = an eye popping 3.6 including a 7 min battery (but not the heavy E-flight 450; see below for more). 

That is an actual Wing Loading of 6.1 oz/sq inch.  Compare to a Precision Aerobatics RC Addiction X, which brags about achieving 8.1 oz Wing Loading and a WCL of 3.7.  The Cap 232 trounces the latest Addiction's numbers - except wingspan.

But wait, that's not the half of it.  The Cap 232 achieves that with a well designed .10 motor, not E-Flites brick 450.  Add a smallish 10x4.6 prop and you can eek out 10 minute flights using a 1300 mAh 3S.  T:W?  How about 2.1 to 1?
The Super Tigre .10 motor's high T:W ratio 
gives the Cap 232 astonishing 3D performance.
PNP cost for the model + motor + ESC + digital servos = $120 + $30 + $30 + $75 (minus $50 LHS discount) = $205.  Compare to $540 for the much lower spec PA Addiction X or $420 for the even lower spec Addiction.

In the Air:

As you've already seen, the maiden did not go well due to Horizon Hobby's dangerous negligence.  I decided not to ding the plane to an F, as I usually due when Horizon puts out an acutely dangerous model (far too often).  The reason is that E-Flite's incompetence is so easily fixed with a little upfront knowledge.  After reading this review, you will likely be safe.

Unfortunately, lethal design flaws are not the only thing wrong with the Cap 232.  The plane has areas of greatness: feather light WCL (much lighter than the Ascent motor glider!), superb power to weight as long as you ignore E-Flite's too-heavy motor recommendation, and nice large throws - but it also has major problems in the air:

  1. Stabilized inverted flight is overly affected by power setting
  2. The Cap 232 has great difficulty holding a knife edge
  3. Simple aileron rolls exhibit mild roll coupling
These two major issues share a single cause: the design thrust line is way off.  The stick motor mount is too high, and not coincident with the center line of the symmetrical wing airfoil.  This induces a severe nose down or up twisting moment whenever power is modulated.  While it is easily trimmed out for upright level flight, and tends to cancel increased lift from increasing airspeed, it works opposite (improperly) when inverted.

Worse, when on a knife edge, the plane wants to pitch down hard (nose away from canopy), exhibiting excessive pitch coupling.  Knife edge loops should be a piece of cake, but are instead onerous to pull off cleanly as the plane rolls out or bends the circle around the Z axis.

Simlarly, the off-axis engine placement creates some dumbbell effect and resultant roll coupling during maneuvers as simple as an aileron roll.  Uhg.

Lastly, high-alpha flight is fairly difficult to stabilize in a Harrier type attitude, though hovers are easy at less than half power (switched to an 11x3.8 for a better altitude connection to the throttle), as long as you can keep the Cap from effortlessly climbing.

All in all, this plane is a disappointment.  Not because of the all-to-common unsafe Horizon Hobby hardware (an unfortunate trend), and not because value is lacking, but simply because it the plane is poorly designed.  I am going to try to move the motor onto the longitudinal axis where it obviously belongs, but the basic structure makes that mod more difficult than it needs to be.

Sooooo much promise; so little reward.  Pretty sad.

Appearance: B-
Not bad for a contra-scale minibat

Airframe: C-
Incredible floater.  Untenable thrust vector placement.

Power System: B-
E-Flite's power system recommendation is too heavy and low T:W.

Build Quality/Durability: F
Lethal design flaw. Unsafe stock push-rods.

Value:  B+
Great performance:price ratio.  Sweet lightweight wing design.

Overall Grade:  C-
Could've been great!  Not aerodynamically pure.  Might be fixable.

Sunday, November 27, 2011

Typhoon 2 3D RTF Flight Review

The Parkzone Typhoon 2 is an excellent 3D trainer. 
...which is probably why they stopped making it. Seriously, I'm not sure why Parkzone stopped Typhoon production.  Ok, it is a little funny looking, but this plane is a lot of fun and flies a lot better than most foamies.  Fortunately, you can still buy one, its just a bit more work to assemble from parts:

Typhoon Build-Up
Landing Gear
Control Horns
Wing set
Horizontal Tail
Motor* 480/.10
30 Amp ESC
+ motor
*$20 more for stock power system
The plane used to ship as an FM bird for $230, so it's quite a bargain today.  Here is the official parts supply website, but other online sources are easy to find and may offer a substantial discount:
(select "Parts & Assessories" then "Parts Listing" then "See All")

On the Ground:

The circular flare over the firewall is perfect 
to accommodate the Trojan/Corsair  mount.
I decided to use an old Trojan 480 motor that I had pulled out in favor of a .10, long ago.  If you also screw the Trojan's nylon engine mount to the Typhoon's plastic firewall, it is a form-fit PNP motor replacement.  Even the cowling appears to have been designed for a 480 sitting on the Parkzone Trojan/Corsair mount, as it flares to accommodate the circular overlap of the mount on the firewall.  The overall length is also a perfect fit.

A Super Tiger .10 would yield more thrust and 1.3 oz less weight in the nose, but would require 4 x .75 inch spacers around 1" bolts, which gives back 0.3 oz and isn't quite as convenient.  If you use the extra thrust it would eat the battery faster, but only on the margin - at the same power setting the low mass design should be a little bit more power efficient.

The Typhoon used to ship with a small brushless motor matched to a reduction gear spinning a large 13.5 x 7 Slo Fly prop for 3D and a 12 x 9 for aerobatics, both at relative low RPM. The 480 is a higher RPM solution, so an 12 x 3.8 Slo Fly is a nice match, and allows a 60-70% throttle hover.

The Parkzone 480 motor is a perfect match for the original 2025 brushless geared Typhoon motor, from weight and power perspective.  The only real difference in the air is the direct drive 480 is a little more responsive and battery efficient.  Total weight in the nose is exactly the same.

In the air, the Typhoon is a ton of fun.  With the control throws knocked down, it is very docile and stays where you put it.  A disciplined intermediate flyer could handle it.  Although it can be flown very mildly, the tail tends to droop at less than half power, and it is not self-righting in any way so beginners should steer clear.

For those looking to improve their aerobatic skills, the Typhoon is very symmetric in the air.  Knife-edge flight is largely uncoupled, but the alignment of the large SFGs can be a source of error. Inverted level flight only demands very slight down-elevator.  The heavy motor is probably the reason for that, the Super Tigre .10 would provide better balance.  Even with the weighty Parkzone 480, the CG is pretty far back compared to mere mortal airplanes, 35% of the mean chord-line or so.

With throws pumped up, the plane's light Wing Loading makes it a rather extreme aerobat and an excellent floater.  The Typhoon has no problem changing direction in an instant.  Walls are well done.  Power on tumbles can maintain altitude in a variety of ways.  Knife edge loops can be pretty tight.

The only real downside to the Typhoon experience is foam imprecision.  The airframe is far from stiff, and as a result, not super precise.  The SFGs in particular seem to bend in the air inducing minor random twists and turns.  The slower the airspeed, the better the plane behaves.  The plane hovers well for its size, but could use the lighter motor to help disarm nose fall off.

Overall, I give the Typhoon high marks for delivering a reasonably high performance 3D experience at an ok price.  Component quality is pretty good too, with entry level digital metal gear servos and an 30 Amp ESC included in the basic package.  It is no wonder Parkzone stopped making it, why sell decent components when they can sell junk in a flashier package?

Appearance: C-
Hmmmm... I've grown to kind of like it.

Airframe: B+
High performance package marred by foam flex.  Floats great.

Power System: B-
The geared brushless works ok.  Add direct drive for responsiveness.

Build Quality/Durability: B+
Strong and survivable for learning.  Decent stock servos.

Value:  B+
Still a little pricey to build up.  Good performance:price ratio

Overall Grade:  B+
The Typhoon is always fun to fly.  What else matters?

Tuesday, November 22, 2011

WWII Warbird Secret Weapon Dogfight

An epic battle is underway.  The challenge: lie, cheat, steal to gain the upper hand... 
Each of these gorgeous warbirds is hiding something.
Each of these WWII classics has a secret they aren't sharing.  In the art and science of aerial combat, there is an unwritten rule: he who wins writes history.  None of these wicked bastards is about to go down easy.  If you aren't cheating you aren't trying--this is about climbing on top of the other two aircraft and beating your chest in victory.

The lineup:

Lockheed P-38 Lightning
Secretly packing a high C rate 4S 2500 mAh under it's slightly modified battery compartment hood (cut 1/4" foam from the rear underside), the Forked Tail Devil tracks arrow-straight at any power setting.  The twin motors pull so hard, one dislodged the two engine mount anchor bolts, requiring a re-glue of the plywood firewall to the foam.  Now with counter-rotating 9x7x3s that spin at a higher RPM than the stock co-rotating 9.5" props, a decrease in prop diameter and increase in prop pitch raises top speed.  One screamin' demon, this P-38 is ready to rumble.

Supermarine Spitfire Mk IX
Now with clipped wings that are true to period, my Spit is more slippery than ever near the top end.  Roll rate is tremendously improved, just the ticket that made the original wing clip design attractive.  A tight battery compartment is barely large enough to wedge a chunky 4 cell 2200 mAH inside the fuselage, but I've managed to push one just far enough forward to keep the CG in check.  This comes at the expense of cooling airflow from the open radiator, from which air is unable to pass through the tight battery fit--but this is war, not history class, suck it up!  I'll reshape the rudder later.

Focke Wulf Fw-190
The butcher doesn't bring it weak.  The stock 4S-capable motor required a new ESC due to a manufacturer-defect resulting in a 3-cell ESC fire.  In retrospect that was a good thing, because 4S has already secretly proliferated to the competition.  Now turning a 4S 2200 mAh battery to keep the wing loading as light as possible, this point defender runs the enemy down like a propaganda-crazed Nazi women scorned.  The engine mount had to be stabilized with expanding Gorilla Glue to keep the higher RPM from shaking it loose.  A 10x8x4-blade prop turns serious torque into serious pull.  The SS Fw-190 just might pack enough punch to win this unfair battle.

Ultimate Warbird Dogfight
43.2" (38")
Clipped Wings
4-Blade Prop
Power System (**est)
2 x 480**
LiPo Cells
Expanded Scoring
Ground views
Aerial Views
Wing Loading
Roll Rate
Aerobatic Quality
Min Turn Radius
Fly-by Impact

Saturday, November 19, 2011

P-38 Counter-Rotation Mod

The Hobby King P-38 did very well in my recent review - but that's even more reason to upgrade the airplane.
The MAS 9x7x3-blade pusher and puller props run about 
$11 each.  The pusher should be installed on the #2 engine
(pilot's right) to minimize P-factor when single engine.
 I've added two upgrades: one big; one small:
  1. Counter-rotating motors and props
  2. Improved nose gear servo
The HK P-38 ships with custom propellers that work well and look great.  Each blade has to be inserted and screwed into the two piece hub.  How hard would it have been to provide three clockwise rotation blades?  Obviously too hard, cause they didn't.

The great news is how easy the Master Airscrew 9x7x3-blade pusher/puller series props fall right into this airplane, while still using the great looking stock spinners.  The only modification required is to slice about 1/8" off the plastic spinner sleeve that slides over the motor shaft.  Once the inner shaft is shortened, the thinner prop depth of the MAS 3-blade installs exactly the same way as the original.

After installing the pusher prop on the pilot's right side motor (engine #2), all that is left to do is switch any two of the three electric motor ESC leads on that side to reverse the motor's spin direction:
Since the original props were 9.5" in diameter, this new MAS config should yield a higher top speed, assuming similar pitch.  Drag from the rudder offset is also gone.

Maybe I'll dip the tips in yellow?

My second upgrade was to swap the cheap nose gear retraction servo to a Hitec Carbonite Micro Feather at a cost of about $15.  My hope is that the longer throw and greater torque will help keep the NG from collapsing when rolling over uneven surfaces.

Total cost to upgrade the P-38: about $37, bringing the TCO to about $175.  This plane flies so well, it remains a bargain.

No more torque and P-Factor!

In the Air:

I thought the P-38 was already a joy - but this mod takes it up another notch.

The plane has a lot of power on 4S.  The MAS 9x7x3 combo increases the top speed, but at the expense of static thrust (which is plentiful).  The plane effectively has unlimited vertical, but it does slow down some on the way to becoming a dot. The crown jewel is arrow-straight tracking at all airspeeds and throttle settings.

This plane has strong aerobatic prowess for a warbird, and the counter rotation makes it even better.  Knife edge flight can be held indefinitely on either edge with some coupling to iron out.  Spins are tight but controllable, upright or inverted, either direction.  Bat turns are impressive.  Loop and roll aerobatics remain symmetrical seven ways to Sunday.

Beautifully behaved; straight as an arrow; airspeed agnostic.  The 38 is a much more cooperative aerobat than it should be.  This counter-rotating twin boom design is on to something special.

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